Production of nitriles from certain olefins and hcn



I our application, Serial am Dec. 14, 1948 UNITE-o STATES PATENT OFFlCPRODUCTIONOF NITRILES FROM CERTAIN I :OLEFINS AND HON Charles R. Harris,Lockport, and Wilbur w. De Atlcy, lfilialaralalls.N..1L,v assignors toE. I. do Pont de 'Nemours=& Company, Wilmington,

Del, a corporation of no Application ms, 1941,

Serial No. 759,300-

1': Claims. (emce -465.3)

1 This invention relates process forthe production of nitriles fromolecertain new compounds obtained thereby;

v to the production ofnitrilesand moreparticularly to anew catalyticThis application is a, continuation-in-part I of v No. 521,666 filedFebruary 9,1944, now abandoned.

Nitriles have reviouslybeen verting oleiins to alkyl sulfates or halides:and

produced by conreacting the latter with analkali metal "cyanide.

More recently, there has been disclosed in U. 8.1%.

2,385,741, a process wherein olefins arereacted with hydrogen cyanideutilizing elevated temper ature and pressure in the presence ofdispersed metal catalyst, preferably copper or cobalt. The vformerindirect process obviously is undesirable J and expensive forcommercial operation. The' latter process requires elevated pressuresand high temperatures, for example, the vpreferred operatingtemperatures are 400 to 750? C. Furthermore, the yields obtained arevery low.

It is one of the objects of this invention to provide a novel processfor the production of nitriles. Another object is to provide a new andimproved process for the conversion of olefinic hydrocarbons tonitrlles. A further object is to provide a new catalytic process forproducing nitriles by the reaction of olefins with hydrogen cyanide inwhich good yields are obtained. An-- other object is to provide novelnitriles which are useful as chemical intermediates. These and otherobjects will be apparent from the ensuing description of the invention.

The above objects are attained in accordance with our invention whichcomprises reacting certain olefinic hydrocarbons with hydrogen cyanidein the vapor phase in the presence of a catalyst consisting of activatedalumina, titania, silica, magnesium silicate or mixtures thereof at 250to 500 C.

The hydrocarbons which may be utilized in accordance with the inventionare those hydrocarbons containing not more than 10 carbon atoms in themolecule and having an aliphatic carbon chain containing one doublebond, said double bond linking a tertiary carbon atom to another carbonatom which may be primary, secondary or tertiary, and hydrocarbonscontaining 3 to 6 carbon atoms in the molecule and having one doublebond, said bond linking a secondary carbon atom to another carbon atomwhich may be primary or secondary.

Illustrative of those hydrocarbons having a double bond linking atertiary carbon atom to another-,1 carbon atom wh ichare satisfactory inpracticing the invention are: .CHFvC CH z. Isobutene CHr CH=C CHi ITrimethyl ethylene;

cmc=C-0H= 2H3 H: Tetramethyl ethylene C Ha CHa-C=CHCCH:

' H; CH;

Diisobutylene CH9=CC4H5 ]Hs Alpha-methylstyrene cni--cH=c-cm53-ethylpentene-2 CH3 CH; CB3 CH=C H-CH-Cm zHi4,5-dimethyl-3ethylheizeue'2 CHaCHg-C=CH3 2-methyl butenc-l CH:CII1-CHzl-=C-CH:

IS-methyl pe'ntcne-Z CH: CH3CH2C=( 1CH z-methyl pentene-Z CH1=CCHCHQ CHCH 2,3-dimethylbutenc-l CH3-CH1CH2C=CHl 2-methy] pentene-l auaeea Ha2-methyl-5-ethyl-heptene-5 CHPC Hr-CH-CHr-QHr-C=CCHI Hi H1 2,6dimethyloctane-2 on. om

p-Methyl alpha methyl styrene Illustrative .of those hydrocarbonscontaining 3 to 6 carbon atoms and having a double bond linkingasecondary carbon atom to another carbon atom are:

CH:CH:=CH: Propylene CHg-CHg-CHFCH:

' Butane-l of gamma-alumina is particularly suitable.

CHrCHrCH=CH-CH:CH5

Hexene-ll CH-CHrCH' -CH:

i-methyl pentene-l cmom-c-cn=cm 3- methyl pentene-l In operating ournovel process, the hydrocarbon vapor and hydrogen cyanide vapor may bepassed together over the catalyst in a heated reactor and thetemperature so controlled that the temperature within the catalyst massis within the range of 250 to 500 C. Although the process may beoperated successfully to produce nitriles at any temperature within therange of 250 to 500 C., we have discovered that optimum results, whenutilizing hydrocarbons having a double bond linking a tertlary'carbonatom, are obtained at temperatures of 380 to 400 C., and it is preferredto operate the invention within this range. Not only are the highestyields and conversions obtained at 380 to 400 C. but also the catalystis -mainta1ned at a high degree of activity for a longer time before itbecomes necessary to regenerate the catalyst. When hydrocarbons having adouble bond linking a secondary carbon atom are utilized, the preferredtemperatures for optimum results are about 25 to 50 C. higher. Forexample, we have discovered that although fair yields may be obtainedwhen operating near the extremes of the 250 to 500 range, the catalysttends to lose activity rapidly and therefore must be regeneratedfrequently if satisfactory operation is to be obtained.

The catalysts which. are useful in the operation of our invention arealumina, titania, silica and magnesium silicate, in activated form, i.e. having surface active properties and which may be prepared bywell-known methods, for example by precipitation as the hydratedmaterial followed by dehydration under controlled conditions. Examplesof these surface active forms are alumina gel and titania gel.- Thecatalysts may be mixed with each other foruse in our invention,impregnated upon each ot er or co-precipitated and in the claims theterm mixtures is intended to include within its scope mixtures of anytwo or more of the catalysts thus obtained. We prefer to utilizeactivated alumina and any of the various grades of activated aluminaavailable on the open .market are satisfactory. We have found thatactivated alumina containing a high proportion We prefer to utilizeactivated alumina as this material is readily available, its use resultsin high yields and conversions and this catalyst may be regeneratedrepeatedly without detectable losses in activity.

Preferably, we utilize the activated catalysts of our invention withoutthe addition of other materials. However, substances having no adverseeflect on the reaction and which do not cause polymerization of thehydrogen cyanide'may be added if desired. The catalysts may be inpowdered form or may be used in the form of beads or lumps when a systemutilizing a stationary catalyst is used. On theother hand, when a fluidcatalyst system is employed, the catalyst size should be such as topermit fluidization under the conditions utilized. For example, we havefound that 80 to 150 mesh alumina is entirely satisfactory when using afluid catalyst system.

Ingeneral, we have found that .for the best operation, the catalystshould be regenerated periodically. When operating with a stationarycatalyst, we have, for example, found it satisfactory to regenerate thecatalyst after about hours operation. The regeneration may be simplyaccomplished by burning out with air at 500 to 550 C. If the temperatureis lower than 500 C., the regeneration may be incomplete and result in asomewhat lower catalyst activity. No loss in catalyst activity has beennoted after burning out 25 to 30 times. When a. fluid catalyst system isemployed, we have found that for best results the catalyst in generalrequires regeneration after 1 to 3 hours; and catalysts thus frequentlyregenerated have been used in such a system during approximately 400hours of operation without a detectable loss in activity.

The ratio of hydrocarbon to hydrogen cyanide may be varied over a widerange with successful results. However, we have found it necessary forbest results to utilize a considerable excess of hydrocarbon, and weprefer to utilize the reactants in the ratio of atleast 3 moles ofhydrocarbon for each mole of hydrogen cyanide. We have found that amolecular ratio of 6 moles of hydrocarbon for each mole of hydrogencyanide is satisfactory. A diluent gas, for example, hydroen or nitrogenmay be utilized if desired, but we have found that the utilization ofexcess hydro- Carbon usually makes it unnecessary to use a diluent gas.

The process of this invention may be operated above or below atmosphericpressure with good results. However, we have found that operation atatmospheric pressure is entirely satisfactory, and it is preferred tocarry out the process at atmospheric pressure.

In a preferred method of operating our invention, we utilize thewell-known fluid catalyst technique as described, for example, in Pier,U. S. P. 1.84.5,058. We have found that higher conversions and yieldsare thus obtained and that the process may be operated with higherspace-time-yields than with a stationary catalyst bed. Thus. we maycarry out the process of our invention by passing the hydrocarbon.vapors and hydrogen cyanide vapors into a vertical reactor containingthe desired catalyst in finely divided form at such a rate that thecatalyst is ma ntained suspended in the reactor in a fluidized state.The optimumconditions described above for operation of the process witha stationary catalyst also may be utilized in the fluidized system.

Since it is desirable, in order to obtain the best results, to utilizean excess of hydrocarbon, it becomes necessary for most economicaloperation to recycle the unconverted hydrocarbon issuing from thereactor when utilizing either stationary or a fluid catalyst. However,we have found that a small amount of by-product ammonia is alwayspresent, and if this is not removed, it usually causes plugging of therecycle system with ammonium salts. We have, therefore. found itdesirable to remove ammonia by scrubbing the gas being recycled with anacid material, for example, sulfuric acid or ammonium acid sulfate,prior to passage back into the reactor.

The products which are obtained in accordance with our novel processwhen reacting diiso- 6 butylene and tetramethylethylene with hydrogencyanide are new compounds.

The product obtained from the reaction of hydrogen cyanide withdiisobutylene is dimethyl neopentyl acetonitrile having the formula;

and having a boiling point, at 760 mm. of mercury, of 178 C., arefractive index, 11 1.4230. The theoretical nitrogen content is 10.07%.Analysis of a sample showed an actual nitrogen content of 10.06%.

Alpha, alpha, beta-trimethyl butyronitrile, the new compound obtained byreacting tetramethylethylene with hydrogen cyanide which has theformula;

II (IIN CH;-C-CH:

CH: Hi

and has a boiling point, at 760 mm. of mercury, of 152 C. and arefractive indexn 1.4100. The calculated nitrogen content is 12.64% andanalysis showed the product to contain 12.59% nitrogen.

The following examples illustrate our invention:

Example 1 A mixture of hydrocyanic acid vapor and isobutene was passedthrough a bed of alumina gel, which had been dried at 400 C., at therates of 500 cc. per minute of hydrocyanic acid and 750 cc. per minuteof isobutene. The temperature in the catalyst bed was maintained at 350to 400 C. The off-gases were condensed and trimethyl acetonitrile wasrecovered from the condensate' by distillation.

After 3.5 hours, the process was stopped and the alumina catalyst washeated in air at 700 to 800 C, to completely burn out organic material.The catalyst then was used in a succeeding run according to the aboveprocedure.

In this manner, four successive runs were carried out, with thefollowing results:

Run Time Yield Per cent 1 Net yield of trimethyl acetonitrile, based onHCN used.

Example 2 Example 3 A catalyst consisting of 300 cc. of 4-10 meshactivated alumina was placed in a 37 mm. 1. d. x 30" quarts tube in afurnace and dried in a current of nitrogen for 3-4 hours at 400 C. A gasmixture of 550 cc. of isobutene, 250 cc. of hydrogen and cc. of hydrogencyanide was passed over this catalyst for five hours while the hot spot"of the catalyst was maintained at 380-400 C. The hydrogen was merelyused as a vehicle for volatilizing a known amount of hydrogen cyanideper minute by bubbling it through a hydrogen cyanide reservoir at C.

The product was collected by condensing in a water cooled condenser, anice trap and a dryice trap. The hydrogen was allowed to escape through acaustic trap. The isobutene that condensed with the product was allowedto warm up and evaporate through the caustic trap. The crude product,trimethylacetonitrile, remaining, was washed several times with dilutecaustic to free it from hydrogen cyanide. Weight oftrimethylacetonitrile recovered, 99.5 g. The caustic trap and washingswere analyzed for hydrogen cyanide and gave 3.7 g. of recoverablehydrogen cyanide. A total of 55.5 g. of hydrogen cyanide was used asdetermined by weighing the vaporizer before and after the run. Theconversion and net yield based on hydrogen cyanide were 58.5% and 62.5%,respectively. The product was dried and distilled at atmosphericpressure. Practically all of it distilled over as puretrimethylacetonitrile boiling at 104-105 C. and melting at 17-18 C.

Example 4 A reaction similar to Example 3 was carried out with astainless steel tube of the same dimensions as the quartz tube. 300 cc.of activated alumina was placed in the tube and dried for 2 /2 hours at380-400 C. in hydrogen. A gas mixture of 550 cc. of isobutene, 250 cc.of hydrogen and 200 cc. of hydrogen cyanide per minute was passed overthe catalyst for 5% hours with the hot spot maintained at 395-415 C. Theproduct was collected and purified as in Example 3. A total of 138 g. oftrimethylacetonitrile was separated from the caustic wash. A total of 98g. of hydrogen cyanide was vaporized and 26.1 g. recovered. Conversionbased on hydrogen cyanide was 45.8% and net yield 62.4%. The product waspale yellow and was purified by simple distillation as in Example 3.

Example 5 Example 3 was repeated except that the hydrogen cyanide wasmetered as a liquid and vaporized in a heated flask without the use ofhydrogen. The hot spot of the catalyst was maintained at 365418 C. forfour hours While 550 cc./min. of isobutene was added and a total of 70g. of hydrogen cyanide was added fairly evenly over the four hourperiod. There was obtained 90 g. of trimethylacetonitrile and 7.5 g. ofhydrogen cyanide was recovered. Conversion based on hydrogen cyanide was42% and net yield 47%.

Example 6 was maintained at sac-403 c. and the gas mix-' ture passedthrough for 3% hours. Total hydrogen cyanide fed was 63 g. and 11.1 g.was recovered. The product was washed free of hydrogen cyanide withcaustic and purified by fractional distillation whereupon 84 g. ofphenyl di- 8 methylacetonitrile boiling at 100106 C. at mm. wasobtained. Conversion based on hydrogen cyanide, 24.7% and net yield,30.0%.

Example 7 the nitrile from diisobutylene boiling at 172-183 C. wasobtained. 20.65 g. of hydrogen cyanide were recovered, conversion basedon hydrogen cyanide was 7.2% and net yield 9%. The purified nitrile, anew compound, has B. P. (760) 178-179 0.; N 1,4230; nitrogen, calc.10.07%,

.found 10.01%, 10.10%.

Example 8 Example 3 was repeated except that 300 cc. of 6-10 meshactivated titania was used as catalyst instead of the alumina. The gasfeed had essentially the same composition as in Example 6. A total of 84g. of hydrogen cyanide was fed during 4.8 hours at 387-445 C. and 37.7g. was recovered. 18.5 g. of trimethylacetonitrile was produced. Basedon hydrogen cyanide, conversion was 7.2% and net yield 13.0%.

Example 9 Example 3 was repeated with 300 cc. of activated silica gelinstead of alumina gel as catalyst. It was operated at 390-415 C. forfive hours with a gas feed composition similar to Example 3. A total of101 g. of hydrogen cyanide was fed during this time and 79.0 g. wasrecovered. A total of 3.3 g. of trimethylacetonitrile was producedwhich, based on hydrogen cyanide, is a conversion of 1.1% and net yieldof 4.6%.

Example 10 An apparatus similar to that used in Example 3 was chargedwith 300 cc. of activated alumina and operated 6 hours at 430-505 C.while a mixture of 250 cc. of hydrogen, 200 cc. of hydrogen cyanide and550 cc. of propylene was passed over the catalyst. A total of 78.5 g. ofhydrogen cyanide was fed and 32.5 g. recovered. Total product afterpurification was 22.5 g. of isobutyronitrile making a conversion of11.2% and a net yield of 19.9% based on hydrogen cyanide.

Example 11 The apparatus of Example 10 was operated with 300 cc. ofactivated alumina at 370408 C. while a mixture of 250 cc. of hydrogen,200 cc. of hydrogen cyanide and 550 cc. of butene-2 was passed throughfor 5.1. hours. Total hydrogen cyanide feed was 68 g. and 45.6 g. wererecovered. Total product was 6.0 g. of methyl ethyl acetonitrile -makinga conversion of 2.9% and a net yield of 8.7% based on hydrogen cyanide.

Example 12 The preceding example was repeated but butene-l instead ofbutane-2 was used. It was operated at 420-450 C. for 2 hours. Totalhydrogen cyanide fed was 27.5 g. of which 4.3 g. were recovered. A totalof 11.7 g. of methyl ethyl acetonitrile was produced with a conversionof 13.6% and net yield of 16% based on hydrogen cyanide.

Example 13 Example 6 was repeated except that 350 cc. oftrimethylethylene was used instead of the alpha- Total product afterpurification by distillation was 52 g. oi dimethyl ethylacetonitrilegiving a conversion of 34.5% and a net yield of 40.7% based on hydrogencyanide.

Example 14 Example 3 was repeated in general except that 300 cc. of 6-8mesh activated magnesium silicate was used. The catalyst was dried undernitrogen for 4 hours and operated for 5 hours at 375-397 C. A total of85.5 g. of hydrogen cyanide was vaporized. A total of 66.4 g. ofhydrogen cyanide was recovered and 37.1 g. of trimethylacetonitrile was.

produced. Conversion was 14.1% and net yield 63.2%, based on hydrogencyanide.

Example 16 This preparation was carried out in a fluid catalyst reactorconsisting of a 2 i. d. glass tube 4 long with a conical bottom andinverted cone top. Exit gases passed through a small glass.

cyclone separator to remove any fine catalyst particles carried from thereactor. The reactor was placed in an electrical furnace for heatcontrol. The reactants were fed as a vapor into the bottom of thereactor at the rate of 14-20 liters per minute. Trimethylacetonitrileand hydrogen cyanide were recovered from the product gases as describedwith the stationary bed catalysts. The hydrogen cyanide was vaporized bypassing a known volume of hydrogen through liquid hydrogen cyanide heldat a constant temperature.

For these experiments the reactor was charged;

with approximately 1500 cc. of activated gammaaluminaof 80-150 mesh. Inthis experiment a total of 360 g. of hydrogen cyanide and approximately4200 g. of isobutene were passed through the reactor in a ratio of 1mole of hydrogen cyanide to 6 moles of isobutene while the catalyst wasmaintained at 385-395 C. The product contained 638 g. oftrimethylacetonitrile and 115, g. of hydrogen cyanide was recoverable.Based on hydrogen cyanide, the conversion was 57.8% and net yield 84.7%.

During this period of reaction of about 2 hours, the catalyst had becomepartially deactivated. Full activity was restored by passing air throughthe catalyst until the carbon containing deposit was burned 011. Thiswas carried out at 500- 550 C. for one hour.

Example 17 I Using the regenerated catalyst from Example 16 andoperating in a, similar manner, 288 g. of hydrogen cyanide and 3620 g.of isobutene were passed through the reactor in the ratio ofapproximately 1 mole of hydrogen cyanide to 6.1 moles of isobutene for atwo-hour period. 530 g. of trimethylacetonltrile was obtained from theprodact and 83.2 g. of hydrogen cyanide was recoverable. Based onhydrogen cyanide, conversion was 59.8% and net yield 84.2%.

Example 18 For this experiment a stainless steel reactor ofapproximately the same dimensions as the glass reactor was used exceptthat it contained a series of stainless steel bailies constructed of V4"mesh wire and spaced three inches apart. It had a stainless steelcyclone in the exit gas line and was preceded by a stainless steelpreheater for raising the temperature of the feed gases'to 250- 300 C.Operating conditions and catalyst were essentially the same as those forthe glass reactor.

During a two-hour period 340.7 g. of hydrogen cyanide and 3740 g. 01isobutene were fed in approximately a molar ratio of 1:5.5. From theproduct 792 g. of trimethylacetonitrile was obtained and 149.3 g. 01'hydrogen cyanide was recoverable. Based on hydrogen cyanide, conversionwas 52.6% and net yield 83.0%. The catalyst was regenerated by burningof! carbon deposits as described under Example 3.

Example 19 The reactor described under Example 18 and the same catalystand general operating procedure was used in reacting 499 g. of hydrogencyanide and 4200 g. of isobutene over a two-hour period. The molar ratioof hydrogen cyanide to isobutene in the feed was approximately 1:43.

During this period 740 g. of trimethylacetonitrile was obtained and174.5 g. of hydrogen cyanide was recoverable. Based on hydrogen cyanide,conversion was 48.2% and net yield 742%.

We claim:

1. Process for the production of nitriles which comprises reacting acompound from the group consisting of hydrocarbons containing not morethan 10 carbon atoms and having an aliphatic chain containing one doublebond, said double bond linking a tertiary carbon atom to another carbonatom and hydrocarbons containing 3 to 6 carbon atoms and having onedouble bond said bond linking a secondary carbon atom to another carbonatom with hydrogen cyanide in the vapor phase in the presence of anon-metallic catalyst selected from the group consisting of activatedalumina, silica, titania, magnesium silicate and mixtures thereof at250-500 C. under substantially atmospheric pressure.

2. The process of claim 1 in which the reaction is carried out at380-400 C. I 3. The process 01' claim 1 in which the molecular ratio ofhydrocarbon to hydrogen cyanide is at least 3 to 1.

4. The process of claim 2 in which the catalyst is activated alumina.

5. The processor claim 2 in which the catalyst is activated alumina andthe hydrocarbon is tetramethyl ethylene.

10. The process of claim 2 in which the catalyst is'maintained in afluidized state throughout the reaction period.

11. The process of claim 2 in which the hydro- 11 carbon vapor andhydrogen cyanide vapor is passed into a reactor at a rate sufficient tomaintaln the catalyst in a fluidized state.

12. The process of claim 2 in which unreacted hydrocarbon is freed fromammonia and recycled.

13. The process of claim 10 in which unreacted hydrocarbon is freed frombyt-product ammonia by scrubbing with an acidic material and recycled.

14. The process for the production of trimethyl acetonitrile whichcomprises reacting hydrocyanic acid with isobutene in the vapor phase ata temperature of about 380 to 400 C. in the presence of a non-metalliccatalyst comprising alumina under substantially atmospheric pressure.

12" mixture containing hydrocyanic acid and isobutene, in the proportionof about 3 moles of isobutene for each mole hydrocyanic acid, overalumina gel'at a temperature of about 380 to 400 5" C. undersubstantially atmospheric pressure.

15. The process for the production of trimethyl 1 acetonitrile whichcomprises reacting hydrocyanic acid with isobutene in the vapor phase ata temperature of about 380 to 400 C. in the presence of alumina gelunder substantially atmos pheric pressure.

16. The process for the production of trimethyl acetonitrile whichcomprises passing a gaseous mixture containing hydrocyanic acid andisobutene, in the proportion of at least one mole of lsobutene for eachmole of hydrocyanic acid, over a non-metallic catalyst comprisingalumina gel at a temperature of about 380 to 400 C. under substantiallyatmospheric pressure.

17. The process for the production of trimethyl acetonitrile whichcomprises passing a gaseous CHARLES R. HARRIS. WILBUR W. DE ATLEY.

REFERENCES CITED The following references areof record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,353,091 Slotterbeck et a1 July4, 1944 2,385,741 Teter Sept. 25, 1945 2,432,532 Mahan Dec. 16, 19472,445,693 Porter et a1 July 20, 1948 FOREIGN PATENTS Number Country Date463,123 Germany July 23, 1928 583,607 Great Britain Dec. 20, 1946728,241 France July 2, 1932 OTHER REFERENCES Haller et al., Compt. rend,vol. 149, page 6 (1909).

Haller et al., Compt. rend., vol. 158, page 302 (1914).

Ziegler et a1., Chem. Abstracts, vol. 26, page 3776, (1932).

